Flooding in Hawaii

On this page you learn what types of flooding are typical in Hawaii and how do you protect yourself, your family and your home. You will also find out more about significant Hawaii floods. Finally, you'll find links to NWS offices that provide forecast and safety information for Hawaii, as well as links to our partners who play a significant role in keeping you safe.

Significant Hawaii Floods

April 19, 1974 Kauai and Oahu Flood

One of the worst flood events in recent history in terms of damage extent and lives lost occurred on the morning of April 19, 1974. An upper level low pressure system helped initiate strong thunderstorms over the islands of Kauai and Oahu, and to a lesser extent on the island of Maui. The most intense rainfall occurred over the north-central portion of Oahu where one rain gage recorded peak rates of 2 inches in 10 minutes, 4.5 inches in one hour, and 10.8 inches in 4 hours. The storm total rainfall amount was 21.2 inches at this location. Rainfall over Kauai was less intense but still significant with a peak 24-hour total of 11.5 inches at Wainiha Valley in northern side of the island. All-time peak stream discharge records were broken at seven sites on Oahu and one site on Kauai based on U.S. Geological Survey data.

On Oahu, flooding killed four people and caused extensive property damage with estimates reaching over $3.7 million (unadjusted dollars). The worst damage occurred in the Haleiwa, Mapunapuna, and Fort Shafter areas of the island where over 100 and businesses were destroyed or damaged. In addition, several hundred vehicles were damaged or destroyed by the flooding and many acres of crops were affected. Flooding on Kauai impacted several areas of the island but the worst conditions were in Wainiha Valley where approximately 100 acres of land were inundated by up to 7 feet of water. An infant drowned in the flood waters and a toddler miraculously survived after being swept downstream several hundred feet. Total property damage on Kauai was estimated to be just under $100,000 (unadjusted dollars).

October 30, 2004 Manoa Flood

In late October 2004, an upper level low pressure system destabilized the lower level trade wind air mass and produced wet conditions across the main Hawaiian Islands, resulting in several flash flood events. One of these floods occurred in the early evening hours of October 30, 2004, as a thunderstorm moved onshore from the east-northeast over the Koolau Mountains and into Manoa Valley. Intense rainfall, with peak rates of 1.29 inches in 15-minutes and 8.71 inches in 6 hours, caused Manoa Stream to quickly overflow its banks in several areas. The worst flooding occurred when a debris-clogged bridge diverted flood waters out of the normal stream channel and sent a flood wave through a residential area and into the University of Hawaii at Manoa campus. Flood waters poured into the basement of Hamilton Library and damaged or destroyed archives containing irreplaceable documents. Several instructional facilities and laboratories with critical experiments also sustained significant damage.

There were no deaths or reported injuries in this flash flood event. The total damage estimate reached $85 million (unadjusted dollars), most of which occurred on the University of Hawaii campus. About 120 homes sustained varying degrees of damage. A foot bridge over Manoa Stream within the mid-valley residential area was destroyed and, as of 2013, not replaced.
Flood waters pushed several vehicles into the trees immediately downstream from the Woodlawn Drive Bridge.

Destroyed footbridge in the mid-valley residential area of Manoa

Flood debris outside of Hamilton Library on the University of Hawaii at Manoa campus
Learn More:

Oahu New Year's Eve Flood, December 31, 1987–January 1, 1988

On the night of December 31, 1987, and through the early morning hours of January 1, 1988, heavy rainfall, with maximum 24-hour totals exceeding 22 inches, drenched east Oahu and produced devastating flash flooding in residential and agricultural areas. The highest rainfall intensities reached 4 inches in 1 hour and 15.7 inches in 6 hours in Maunawili. Most of the damage occurred as a result of flash flooding and associated debris flows in Hahaione, Niu, and Kuliouou Valleys.

In many areas, the debris flows clogged existing drainage systems, which forced flood waters out of their channels and caused severe damage to homes and roads. A rapid rise in water level within the Kawainui Marsh overtopped a protective levee and inundated a portion of the Coconut Grove community near Kailua with several feet of water.

There were no flood-related deaths or injuries, an amazing fact considering the high amount of traffic with the New Year’s celebrations in full swing. Property damage estimates totaled about $35 million (unadjusted dollars) and over 500 homes were either destroyed or damaged by flood waters.

Approximately 2800 people were evacuated and 72 were left homeless.
Learn More:

The Anahola Flood, December 14, 1991

A low pressure system west of the main Hawaiian Islands helped generate an area of persistent heavy rainfall over the northeastern slopes of Kauai during the early morning hours of December 14, 1991. The Anahola Stream basin took the brunt of the storm with a maximum event rainfall total of 22 inches and peak rainfall rates of 6.7 inches in 1 hour and 11.6 inches in 2 hours recorded by NOAA/NWS rain gages.

A U.S. Geological Survey stream gage measured a record peak flow of 21,000 cubic feet per second (cfs) within a stream channel capable of handling only 4,000 cfs. The last time a flood of this magnitude occurred in Anahola was January 25, 1956, which involved a peak flow of 19,600 cfs. Significant damage also occurred at several locations along Kapaa Stream south of Anahola, and significant inundation occurred in low-lying areas of Kapaa town.
The overflow of Anahola Stream killed three people and destroyed six homes. Another individual died from flood waters in the Moloaa area north of Anahola. The damage estimate totaled $7 million (unadjusted dollars). Just over half of the total was due to the loss of public property and infrastructure. Civil Defense officials documented 180 homes destroyed or damaged by the flooding.

November 1-2, 2000 Southeast Big Island Flood

The November 2000 flash flood event on the Island of Hawaii, the Big Island, produced the largest single-day rainfall total ever recorded on the island and the second largest 24-hour total in the state’s history. This record-breaking event came about from the ideal combination several factors needed for heavy rainfall production: Extremely moist low level air provided by the remnant of a tropical cyclone, cool and divergent air aloft to support tall thunderstorm development, and mountainous terrain to trigger and anchor thunderstorm cores.

Heavy rainfall initiated over the Hilo area during the night of November 1 then shifted into the Puna and Kau Districts on the morning of November 2. Peak rainfall intensities were 4.56 inches in 1 hour at Hilo Airport, 22.25 inches in 6 hours at Kapapala Ranch, and 37.02 inches in 24-hours, also at Kapapala Ranch. Rainfall at these intensities quickly overwhelmed existing stream channels and carved out new channels where none previously existed.
Although the press reported several water rescues, there were no serious injuries or deaths from the flash flood event. Officials reported the total damage estimate to be approximately $70 million (unadjusted dollars), mostly to roads, bridges, and other infrastructure. Several of the bridges destroyed in the flood were along the Mamalahoa Highway, the only direct route between the city of Hilo and the town of Pahala. The alternate route, around the west side of the island, adds a considerable amount of travel time and distance to the journey. The American Red Cross reported nearly 300 homes were destroyed or damaged and the Federal Emergency Management Agency reported over 2,000 people registered for disaster assistance.

Komohana Ave., a major thoroughfare in the city of Hilo, was severed by massive flooding at the Alenaio Stream Bridge.

Severe runoff carved out a new channel through Kapapala Ranch near the town of Pahala. A rain gage at this ranch recorded the peak storm rainfall of more than 37 inches in 24-hours and more than 22 inches in a 6-hour period.

Flood waters from Waiakea Stream in upper Hilo swept this home off its foundation and placed it in the middle of a public road.

Flash Flooding

Flash flooding is a rapid and extreme flow of high water into a normally dry area, or a rapid water level rise in a stream or creek above a predetermined flood level, beginning within six hours of the causative event (i.e., intense rainfall, dam failure, ice jam). More information...

River Flooding

River flooding occurs when river levels rise and overflow their banks or the edges of their main channel and inundate areas that are normally dry. More information...

Tropical Systems and Coastal Flooding

At any time of year, a storm from over the ocean can bring heavy precipitation to the U.S. coasts. Whether such a storm is tropical or not, prolonged periods of heavy precipitation can cause flooding in coastal areas, as well as further inland as the storm moves on shore. More information...

Debris Jams

A back-up of water into surrounding areas can occur when a river or stream is blocked by a build-up of ice or other debris. Debris Jam: A back-up of water into surrounding areas can occur when a river or stream is blocked by a build-up of debris. More information...

<

Dry Wash

When heavy rain falls over extremely dry land, the water rushes towards low-lying areas, which may include dried up canyon or river beds. This can quickly turn a dry channel into a raging river.More information..

Dam Breaks/Levee Failure

A break or failure can occur with little to no warning. Most often they are caused by water overtopping the structure, excessive seepage through the surrounding ground, or a structural failure. More information...